302系列的探测器都是常开的系统，有135华氏度（57摄氏度）和194华氏度（90摄氏度）两种定温度等级。 302-EPM-194 
302-EPM-135感温棒
All 302 Series Detectors are normally open devices and are available in either 135°F (57°C) or 194°F (90°C) ratings. Each unit is constructed with a high expansion .040 anodized aluminum （氧化铝）sensing shell and fine silver contacts which are hermetically seaLED to ensure reliable operation. Electrical Rating （额定电功率）6-28 VDC, 1 amp. (all models) 大发机电供感温棒
302-135- Interior, Vertical Mounting Fixed Temperature 135°F Maximum Spacing - UL 50' x 50' 
302-194 - Interior, Vertical Mounting Fixed Temperature 194°F Maximum Spacing - UL 50' x 50' 
这款应该是室内使用 

302-ET-135 - All Weather, Vertical Mounting Fixed Temperature 135°F Maximum Spacing - UL 50' x 50' 
302-All Weather, Vertical Mounting Fixed Temperature 194°F Maximum Spacing - UL 50' x 50' 

这款是的环境使用 
302-AW-135 - Moisture and Dust Proof, Vertical Mounting Fixed Temperature 135°F Maximum Spacing - UL 50' x 50' 
302-AW-194 - Moisture and Dust Proof, Vertical Mounting Fixed Temperature 194°F Maximum Spacing - UL 50' x 50' 

这款是潮和尘